Chapter 1 of 530% of exam
Core Trades
A General Building (B) contractor coordinates the specialty trades that make a structure livable and durable. This chapter reviews the code fundamentals a B contractor must understand to supervise concrete, electrical, plumbing, HVAC, roofing, weatherproofing, and site work.
Concrete
Concrete strength is specified in pounds per square inch (psi) and reached through proper mix design, placement, and curing. Reinforcing steel must be positioned with enough cover to protect it from corrosion, and cold joints and honeycombing are avoided through controlled placement and consolidation. A B contractor confirms the mix, slump, and rebar layout match the approved plans before the pour.
Minimum residential strength
Concrete for foundations, slabs, and footings in most residential work is specified at a minimum of 2,500 psi at 28 days, with exposed or severe-weather locations often requiring 3,000 psi or more.
2025 CA Residential Code Table R402.2Rebar cover
Reinforcing steel cast against and permanently exposed to earth needs about 3 inches of concrete cover; formed surfaces exposed to weather typically need 1.5 to 2 inches.
2025 CA Building Code Chapter 19Anchor bolt embedment
Sill-plate anchor bolts are commonly 1/2-inch diameter embedded at least 7 inches into the concrete, spaced no more than 6 feet apart with a bolt within 12 inches of each plate end.
2025 CA Residential Code R403.1.6Curing
Fresh concrete must be kept moist and protected for several days—commonly a minimum of 3 to 7 days—so it reaches design strength rather than drying and cracking prematurely.
2025 CA Building Code Chapter 19Footing depth below frost/grade
Footings must bear on undisturbed soil and extend below the frost line for the jurisdiction, with a minimum footing depth typically no less than 12 inches below undisturbed ground.
2025 CA Residential Code R403.1.4Electrical
California electrical work follows the California Electrical Code (CEC, Title 24 Part 3), which is based on the National Electrical Code. A B contractor must recognize proper conductor sizing, grounding, and outlet placement even when a licensed electrician performs the installation. Ground-fault and arc-fault protection are central to modern residential safety.
GFCI locations
Ground-fault circuit-interrupter protection is required for receptacles serving kitchens, bathrooms, garages, outdoors, crawl spaces, and areas near water.
2025 CA Electrical Code Article 210AFCI protection
Arc-fault circuit-interrupter protection is required for most 120-volt branch circuits serving living areas such as bedrooms, living rooms, and hallways.
2025 CA Electrical Code Article 210Kitchen counter receptacles
Counter receptacles are placed so no point along the counter is more than 24 inches from an outlet, meaning spacing generally does not exceed 4 feet apart.
2025 CA Electrical Code Article 210Working clearance
A clear working space at least 30 inches wide and 36 inches deep must be kept in front of electrical panels and equipment for safe service.
2025 CA Electrical Code Article 110Conductor color/grounding
Grounded (neutral) conductors are white or gray and equipment grounding conductors are green or bare; the system must be bonded to a grounding electrode such as a ground rod or the building steel.
2025 CA Electrical Code Article 250Plumbing
Plumbing installations follow the California Plumbing Code (CPC, Title 24 Part 5). Drain, waste, and vent (DWV) systems rely on correct slope, trap seals, and venting to move waste and keep sewer gases out of the building. Water supply must be sized and protected against contamination through backflow prevention.
Drain slope
Horizontal drain piping generally slopes at least 1/4 inch per foot for pipes 2.5 inches and smaller; larger pipes may slope 1/8 inch per foot.
2025 CA Plumbing Code Chapter 7Trap seal
Every plumbing fixture needs a water-seal trap with a seal depth of 2 to 4 inches to block sewer gas, and each trap must be vented.
2025 CA Plumbing Code Chapter 10Cleanouts
Cleanouts are provided at changes of direction and at intervals along drain lines so blockages can be cleared, and they must remain accessible.
2025 CA Plumbing Code Chapter 7Water heater relief valve
A temperature and pressure (T&P) relief valve is required on water heaters, with a discharge pipe run down to within 6 to 24 inches of the floor or to the exterior.
2025 CA Plumbing Code Chapter 5Backflow protection
Potable water must be protected from cross-connections using air gaps or backflow preventers so contaminated water cannot siphon back into the supply.
2025 CA Plumbing Code Chapter 6HVAC
Heating, ventilation, and air-conditioning work follows the California Mechanical Code (CMC, Title 24 Part 4) plus the Energy Code for efficiency. Combustion appliances need adequate combustion air and safe venting, while ducts must be sealed and sized to deliver design airflow. A B contractor verifies clearances to combustibles and proper condensate handling.
Combustion air
Fuel-burning appliances in confined spaces require openings to supply combustion air—commonly two openings, one high and one low, sized to the appliance's total input rating.
2025 CA Mechanical Code Chapter 7Duct sealing and R-value
Ducts must be sealed against leakage and insulated—supply and return ducts in unconditioned space typically need at least R-6 to R-8 insulation.
2025 CA Energy Code (Title 24 Part 6)Condensate drainage
Cooling coils and condensing furnaces need a condensate drain, and a secondary drain or drain pan is required where overflow could damage the building.
2025 CA Mechanical Code Chapter 3Flue clearance and termination
Vents and flues must maintain listed clearances to combustibles and terminate above the roof, generally at least 2 feet above any part of the building within 10 feet.
2025 CA Mechanical Code Chapter 8Ventilation air
Dwellings require mechanical ventilation for indoor air quality, with whole-house ventilation rates set by the Energy Code and local exhaust in kitchens and bathrooms.
2025 CA Energy Code (Title 24 Part 6)Roofing
Roof assemblies shed water through correct slope, underlayment, flashing, and fastening. Material choice—asphalt shingle, tile, metal, or single-ply—depends on slope and fire rating. In California, wildfire-prone zones demand Class A assemblies and ember-resistant details.
Minimum slope for shingles
Asphalt shingles are limited to roofs with a slope of 2:12 or greater; from 2:12 up to 4:12 a double-layer underlayment is required.
2025 CA Building Code Chapter 15Underlayment
At least one layer of approved underlayment is installed under roofing, with an ice-barrier or self-adhering membrane used where required by climate.
2025 CA Building Code Chapter 15Flashing
Flashing is required at valleys, wall intersections, chimneys, and penetrations to direct water away from joints and prevent leaks.
2025 CA Building Code Chapter 15Class A fire rating in WUI
In wildland-urban interface fire areas, roof coverings must be Class A rated and assemblies must resist ember intrusion at eaves and valleys.
2025 CA Building Code Chapter 7AFastening
Shingles are fastened with the number of nails specified by the manufacturer—commonly 4 to 6 nails per shingle—increased in high-wind areas.
2025 CA Building Code Chapter 15Insulation & Weatherproofing
The building envelope keeps conditioned air in and water out. Insulation R-values are set by the Energy Code and climate zone, while a continuous water-resistive barrier and proper flashing keep the wall assembly dry. Air sealing and vapor control prevent condensation and mold.
Wall and ceiling R-values
Minimum insulation levels depend on climate zone; typical wood-framed walls require around R-13 to R-21 and ceilings/attics around R-30 to R-49.
2025 CA Energy Code (Title 24 Part 6)Water-resistive barrier
Exterior walls need a water-resistive barrier behind the cladding—at least one layer, and two layers of Grade D paper behind stucco applied over wood-based sheathing.
2025 CA Building Code Chapter 14Flashing integration
Window and door flashing must lap over the layer below in shingle fashion so water drains outward, and pan flashing is used at sills.
2025 CA Building Code Chapter 14Air sealing
The building envelope must be sealed at penetrations, top and bottom plates, and joints to limit air leakage, verified during Energy Code compliance.
2025 CA Energy Code (Title 24 Part 6)Attic and crawl ventilation
Vented attics and crawl spaces generally require net free ventilation area of about 1/150 of the area, reducible to 1/300 with proper vent balance or vapor control.
2025 CA Residential Code R806Earthwork & Surveying
Site work sets the foundation for everything above it. Grading must move water away from the structure, and fill must be compacted to a specified density to support foundations without settling. Setbacks, property lines, and elevations are confirmed by survey before construction begins.
Drainage away from foundation
The finished grade must slope away from the building—commonly a minimum fall of 6 inches within the first 10 feet, roughly a 5 percent slope.
2025 CA Residential Code R401.3Compaction
Structural fill supporting foundations is compacted in lifts to a specified relative compaction, often 90 percent or more, verified by soils testing.
2025 CA Building Code Chapter 18Cut and fill slopes
Permanent cut and fill slopes are generally no steeper than 2 horizontal to 1 vertical unless a soils report justifies a steeper slope.
2025 CA Building Code Appendix JFoundation setback from slopes
Foundations near descending slopes must be set back from the slope face—commonly one-third of the slope height, up to a defined maximum—to keep bearing stable.
2025 CA Residential Code R403.1.7Property lines and setbacks
Before excavation, verify property corners, easements, and required yard setbacks against the approved site plan to avoid encroachment.
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